It’s been well established on This Is Us that Kevin and Randall don’t exactly see eye to eye. Throughout their childhoods, they never really acted like brothers. Randall was doing his own thing at a special school for smart kids, while Kevin was the popular jock of his school. In their older age, though, the two have been getting closer, and finally, Kevin put Randall first — he even missed the opening night of his play to be there for his brother.
Randall is under a lot of stress. In addition to continuing to deal with the stress of William dying, he’s recently suffered some setbacks at work, not due to any fault in his abilities but because he has so much on his plate. Randall, who prides himself on being able to do it all, isn’t taking well to this, so much so that he’s internalized the stress into hand tremors and nervous breakdowns. Apparently, he’s done it before — his wife, Beth, told William that Randall once stressed himself out so much that he went temporarily blind. Kevin may be the most self-centered of the Pearson bunch, but he’s seen this behavior before in Randall when they were teens, and so he knows what’s coming.
On the opening night of Kevin’s new play, Randall gets the news that his father doesn’t think he has that long to live, and he also blows a big presentation at work. After Randall calls Kevin to tell him he won’t make it to his play (since he’s in his office having a breakdown), Kevin knows what to do. He has to, as Miguel says, do what his father would do, and that’s go help Randall. A flashback of Randall having a panic attack as a teen showed what Kevin did back then — he ignored him. But today, Kevin ran out on the first scene of his show to Randall’s office, where he found Randall in a ball on the floor and scooped him up into his arms to comfort him.
While I do feel bad for Sloane, the play’s writer, about the perhaps blown chance for her play (there was supposed to be a New York Times critic there, after all), this act of love is just the next step in Kevin’s maturation. He hasn’t always been there for his family, and running (literally) to Randall in a time of need is exactly what true brothers would do for each other. The show will go on, but Randall needed Kevin, and he finally was there to give his brother support.